Piezoelectric films provide the ability to generate an electric charge in response to applied mechanical stress and vice versa. The piezoelectric films can be used in many applications including, e.g., filters.
Piezoelectric planar thin films often have strong vertical coupling, but weak lateral coupling, e.g., AlN. Filters designed using vertical coupling of such a planar thin film are sensitive to film thickness variation. On the other hand, filters designed using lateral coupling are insensitive to film thickness variation but are hampered by weak piezo response.